I like to use the E-M5 in manual mode with auto ISO. It lets me control the two variables of the exposure triangle I'm most concerned about, and at the same time releaves me from having to factor in ISO as a third factor.

However, I haven't found a way to set exposure compensation on the E-M5 in this mode. I think Pentax allows it in its TAv mode (aperture and shutter mode), and I think some high end Nikons allow it too. This would be a very useful feature and should be doable with a firmware fix.